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Use C++11 explicit conversion operator if available

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[SVN r83210]
This commit is contained in:
Beman Dawes
2013-02-28 20:55:07 +00:00
parent 87130d1d73
commit 08ea984237
6 changed files with 41 additions and 31 deletions
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39
doc/reference.html
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@ -452,7 +452,7 @@ error_code</code> synopsis</a></h3>
cont error_category &amp; category() const noexcept;
error_condition default_error_condition() const noexcept;
string message() const;
operator unspecified-bool-type() const;
explicit operator bool() const noexcept;
private:
int val_; // <i>exposition only</i>
@ -517,20 +517,10 @@ error_code</code> observers</a></h3>
<pre><code>string message() const;</code></pre>
<blockquote>
<p><i>Returns:</i>&nbsp; <code>category().message( value())</code>.</p>
<p><i>Throws:</i> Nothing.</p>
</blockquote>
<pre>operator unspecified-bool-type() const;</pre>
<pre>explicit operator bool() const noexcept;</pre>
<blockquote>
<p><i>Returns:</i> if <code>value() != 0</code>, returns a value that will evaluate
<code>true</code> in a boolean context; otherwise, returns a value that will
evaluate <code>false</code> in a boolean context. The value type returned shall
not be convertible to <code>int</code>.</p>
<p><i>Throws:</i> nothing.</p>
<p><i>[Note: </i>This conversion can be used in contexts where a <code>bool</code>
is expected ( e.g., an <code>if</code> condition ); however, implicit conversions
( e.g., to <code>int</code>) that can occur with <code>bool</code> are not
allowed, eliminating some sources of user error. One possible implementation
choice for this type is pointer-to-member. <i>--end note ]</i></p>
<p><i>Returns:</i> <code>value() != 0</code>.</p>
</blockquote>
<h2><a name="Class-error_condition">Class <code>error_condition</code></a></h2>
<p>The class <code>error_condition</code> describes an object used to hold
@ -560,10 +550,10 @@ implementation specific. <i>--end note ]</i></p>
void clear() noexcept;
// observers:
int value() const noexcept;
const error_category &amp; category() const noexcept;
string message() const;
operator unspecified-bool-type () const noexcept;
int value() const noexcept;
const error_category&amp; category() const noexcept;
string message() const;
explicit operator bool() const noexcept;
private:
int val_; // <i>exposition only</i>
@ -626,18 +616,9 @@ observers</a></h3>
<blockquote>
<p><i>Returns:</i> <code>category().message( value() )</code>.</p>
</blockquote>
<pre>operator unspecified-bool-type () const;</pre>
<pre>explicit operator bool() const noexcept;</pre>
<blockquote>
<p><i>Returns: </i>If <code>value() != 0</code>, returns a value that will
evaluate <code>true</code> in a boolean context; otherwise, returns a value
that will evaluate <code>false</code>. The return type shall not be
convertible to <code>int</code>. </p>
<p><i>Throws:</i> Nothing.</p>
<p><i>&nbsp;[ Note:</i> This conversion can be used in contexts where a <code>bool</code>
is expected ( e.g., an if condition ); however, implicit conversions ( e.g., to
<code>int</code>) that can occur with <code>bool</code> are not allowed,
eliminating some sources of user error. One possible implementation choice for
this type is pointer to member. <i>--end note</i> <i>]</i></p>
<p><i>Returns: </i> <code>value() != 0</code>. </p>
</blockquote>
<h2><a name="throws-object"><code>throws</code> object</a></h2>
<pre>extern error_code throws;</pre>
@ -812,7 +793,7 @@ application program interfaces.</p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%B %d, %Y" startspan -->February 27, 2013<!--webbot bot="Timestamp" endspan i-checksum="41547" --> </font>
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%B %d, %Y" startspan -->February 28, 2013<!--webbot bot="Timestamp" endspan i-checksum="41551" --> </font>
</p>
<p><EFBFBD> Copyright Beman Dawes, 2006, 2007, 2008, 2013</p>

14
include/boost/system/error_code.hpp
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@ -270,6 +270,12 @@ namespace boost
const error_category & category() const BOOST_SYSTEM_NOEXCEPT { return *m_cat; }
std::string message() const { return m_cat->message(value()); }
# ifndef BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS
explicit operator bool() const BOOST_SYSTEM_NOEXCEPT
{
return m_val != 0;
}
# else
typedef void (*unspecified_bool_type)();
static void unspecified_bool_true() {}
@ -282,6 +288,7 @@ namespace boost
{
return m_val == 0;
}
# endif
// relationals:
// the more symmetrical non-member syntax allows enum
@ -357,6 +364,12 @@ namespace boost
error_condition default_error_condition() const BOOST_SYSTEM_NOEXCEPT { return m_cat->default_error_condition(value()); }
std::string message() const { return m_cat->message(value()); }
# ifndef BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS
explicit operator bool() const BOOST_SYSTEM_NOEXCEPT
{
return m_val != 0;
}
# else
typedef void (*unspecified_bool_type)();
static void unspecified_bool_true() {}
@ -369,6 +382,7 @@ namespace boost
{
return m_val == 0;
}
# endif
// relationals:
inline friend bool operator==( const error_code & lhs,

4
test/Jamfile.v2
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@ -25,10 +25,10 @@ project
: # command line
: # input files
: # requirements
<link>static
<test-info>always_show_run_output <link>static
]
[ run error_code_test.cpp
: : : <link>shared : error_code_test_shared
: : : <test-info>always_show_run_output <link>shared : error_code_test_shared
]
[ run error_code_user_test.cpp
: : : <link>static

11
test/error_code_test.cpp
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@ -59,6 +59,17 @@ namespace
int main( int, char ** )
{
#ifdef BOOST_NO_CXX11_NOEXCEPT
std::cout << "BOOST_NO_CXX11_NOEXCEPT is defined" << std::endl;
#else
std::cout << "BOOST_NO_CXX11_NOEXCEPT is not defined" << std::endl;
#endif
#ifdef BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS
std::cout << "BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS is defined" << std::endl;
#else
std::cout << "BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS is not defined" << std::endl;
#endif
std::cout << "Conversion use cases...\n";
error_condition x1( errc::file_exists );
//error_code x2( errc::file_exists ); // should fail to compile

2
test/system_msvc/system_dll/system_dll.vcxproj
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@ -20,12 +20,14 @@
<ConfigurationType>DynamicLibrary</ConfigurationType>
<UseDebugLibraries>true</UseDebugLibraries>
<CharacterSet>Unicode</CharacterSet>
<PlatformToolset>v110</PlatformToolset>
</PropertyGroup>
<PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">
<ConfigurationType>DynamicLibrary</ConfigurationType>
<UseDebugLibraries>false</UseDebugLibraries>
<WholeProgramOptimization>true</WholeProgramOptimization>
<CharacterSet>Unicode</CharacterSet>
<PlatformToolset>v110</PlatformToolset>
</PropertyGroup>
<Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
<ImportGroup Label="ExtensionSettings">

2
test/system_msvc/system_error_test/system_error_test.vcxproj
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@ -20,12 +20,14 @@
<ConfigurationType>Application</ConfigurationType>
<UseDebugLibraries>true</UseDebugLibraries>
<CharacterSet>Unicode</CharacterSet>
<PlatformToolset>v110</PlatformToolset>
</PropertyGroup>
<PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">
<ConfigurationType>Application</ConfigurationType>
<UseDebugLibraries>false</UseDebugLibraries>
<WholeProgramOptimization>true</WholeProgramOptimization>
<CharacterSet>Unicode</CharacterSet>
<PlatformToolset>v110</PlatformToolset>
</PropertyGroup>
<Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
<ImportGroup Label="ExtensionSettings">